The present invention refers to a combination instrument for automotive vehicles in which different indicating instruments, indicating fields and control and warning lights and, possibly, operating parts as well as electric and electronic equipment parts are arranged in a common housing and covered by a common transparent glass.
Such combination instruments have been known for a long time and are used to check different functions of an 38tomotive vehicle instead of the previously customary individual instruments. For this purpose, depending on the amount of equipment, they contain, for instance, a tachometer, odometer, speedometer, fuel indicator, cooling-water temperature indicator, clock, warning lights for oil pressure, generator, high beam, direction-of-travel indicators and the like, such as, for instance, monitoring and computing systems together with their display systems, and they are arranged in the vehicle, in each case within the field of view of the driver, in a suitably shaped instrument holder which, in its turn, is fastened to the body.
Electrically controlled displays are being used to an increasing extent in such combination instruments, they making possible, in addition to greater freedom in development, a more intelligent control and thus more precise or more meaningful displays. The control is effected, in general, by the use of microprocessors or highly integrated circuits which are specific to the use. The digital pulse trains which are processed therein have very steep flanks and are also of high frequency. As a result, they produce disturbing radio frequencies which, upon operation of the vehicle may affect other electronic systems present or make radio reception or radio communication difficult. At the same time however, these trains of pulses are also sensitive to disturbances from the outside. Such disturbances may come from other electronic systems of the high-voltage ignition system even of other vehicles, or from strong radio or television transmitters in the vicinity.
In principle, there is furthermore continuous interest in seeing to it that the equipment for automotive vehicles takes up less space so as to increase the room available for the passengers.
While a housing with connection terminals which are impervious to high frequencies is known (Federal Republic of Germany OS No. 35 15 910), it involves a junction or splitter for cable television systems with a network of coaxial cables.